Surgical thread cutters of this kind are utilized to cut a thread material that is used for intracorporeal sutures. It has been found that it is difficult to cut the thread material with the dissecting scissors normally used for cutting tissue. It has been found in particular that the threads get caught in the scissors.
DE 92 14 580.9 U1 discloses a surgical thread cutter which has a sharp blade that moves toward a flat anvil and thereby cuts the thread. For this purpose, blade and anvil are movable relative to one another; the movement is controlled via handle elements such as those ordinarily used in medical scissors, which are joined to one another via a hinge. The anvil has a slot into which the sharp blade can travel, thus cutting through the thread which is pressed against the anvil.
The applicant's company brochure entitled "Endoskopische Chirurgie, 2. Ausgabe 1/94, Kapitel 8, Naht und Ligatur, Seite NH 4 A" [Endoscopic surgery, 2nd edition 1/94, Chapter 8, Sutures and ligatures, page NH 4 A] makes known a surgical thread cutter using the aforementioned Scarfi principle, in which the blade is received so as to move back and forth in a shaft at whose distal end the anvil is arranged. A rod-shaped actuation element joined to the blade passes through the shaft, and that element is joined at the proximal end to an annular handle element. Extending parallel to the shaft at the proximal end, i.e. parallel to the shaft axis, is a spring which braces at one end against the annular handle element and at the other end against a further handle element mounted in stationary fashion on the shaft. The spring is preloaded in such a way that the annular handle element, together with the actuation element and the blade mounted thereon, is pushed away from the anvil, so that space exists between the blade edge and the anvil so as to introduce between the blade and anvil the thread that is to be cut through. To cut through the thread, the distal end of the thread cutter is brought against the thread in such a way that the latter ends up between blade and anvil, the thread cutter itself being introduced, for example, through a trocar into the body. To cut through the thread, the annular handle element at the proximal end is displaced in the distal direction relative to the stationary handle element against the force of the spring, thus moving the blade toward the anvil and cutting through the thread received between them.
DE 42 04 051 C2 discloses an anvil scissors for surgical purposes in which the blade is arranged so that as a function of the thread thickness and the material being cut, the greater the resistance presented to closure of the blade by the material being cut, the stronger the pulling cut. In this context the blade is pivotable about an axis, and movable toward and away from the anvil.
DE 91 09 097 U1 discloses a retaining forceps which contains a spring which generates a preload in order to act upon the two forceps arms in the closing direction. This is a thread holding apparatus. A retaining apparatus serves to displace one forceps arm.
DE 91 12 301 U1 discloses a needle holder which has a rod that is surrounded by a sleeve which is movable axially relative to the rod. The sleeve is displaceable, and is preloaded by a spring against a radial contact surface.
Documents U.S. Pat. Nos. 3,802,074, 3,328,876, and 3,372,477 concern thread cutters in which the blade can be moved back and forth along a shaft-like part, specifically by the hand or a finger of the actuating person who is holding the thread cutter in his or her hand. The cutting movement and the cutting action are thus determined by the particular individual hand strength and dexterity of the operator.
It has been found in practical use that the anvil can press the thread against the anvil and push the latter, without cutting through it, into the slot in the anvil rather than cutting through the thread. In this context, the blade can get caught on the thread in such a way that the force of the spring is not sufficient to pull the blade back away from the anvil.
In addition, it has been found in disadvantageous fashion that the skill of the operator substantially determines whether the thread can be cut through with only a single blade movement, or whether several movements are necessary for the purpose. In any event, it has been found that close attention is required when cutting through the thread.